The present invention relates generally to trim cutting. More particularly, the invention relates to an apparatus and method for trimming cloth, vinyl and plastic from around the periphery or along a contour of a workpiece such as vehicle interior quarter panels, headliners and the like.
Present day automotive interiors are usually manufactured by vacuum forming a vinyl or plastic covering around a substrate of processed wood, cardboard or other natural or synthetic materials. The vacuum forming process involves wrapping the vinyl or plastic covering around the substrate, leaving a certain excess covering to be later trimmed. The vinyl or plastic is then heated and a vacuum is applied to cause the covering to conform closely to and adhere to the substrate. After the heated part has cooled, the edges of the covering must be trimmed so the end product will have a neat appearance. In many cases, the contour of the substrate, which corresponds generally to the contour of the end product, is an irregular or complex-shaped owing to the physical dimensions of the vehicle interior. Because of this complex shape, the edges of the covering may be folded back upon themselves or pleated, meaning that in some places the trimming must be made through several layers of material, whereas in other places the trimming is only through a single layer. Also, in trimming away the excess or offall, care must be taken to avoid cutting into or scoring the substrate. A score in the substrate shows up as a blemish line in the end product and can also structurally weaken the part.
Because of these difficulties, present day manufacturing processes still rely on hand trimming of vehicle interior parts. This adds considerably to the manufacturing time and cost of the vehicle. Punch presses have been used successfully to punch holes through the covering and substrate for mounting door handles, window handles and the like. These punches do not work satisfactorily in trimming operations, because it is difficult to predict where multiple folds in the covering will appear and because it is difficult to properly regulate the cutting force to trim the covering without damaging the substrate.
The present invention overcomes the foregoing difficulties and provides an automated apparatus for trimming along a contour of a workpiece. The apparatus and method encompassed by the invention thus eliminate costly and time consuming hand trimming of vacuum formed vinyl interior parts.
In accordance with the invention, a blade assembly is positionable at least partially along a line defined by the contour to be trimmed. The blade assembly comprises a plurality of blade segments arranged side-by-side and along the line defined by the contour. A means is provided for sequentially pressing the blade segments into cutting contact with the workpiece, thereby causing the blade segments to trim the workpiece. A means is also provided for urging the blade segments out of cutting contact with the workpiece after the trimming has been effected.
The cutting blade assembly comprises a plurality of elongated blade segments, each segment having a longitudinally extending shaft and a cutting blade tip. The segments are substantially greater in length than width, the width being nominally 0.187 inches. The blades segments are positioned side-by-side in order to follow a contour to be trimmed and are individually movable between a resting position and a longitudinally displaced cutting position. Each of the segments has an aperture therein. The apertures are generally aligned with one another when the segments are aligned in the resting position. A tension wire is threaded through the apertures to join the segments together. A spring is connected to the tension wire for placing the tension wire under tension and for thereby causing the segments to return to the resting position after being displaced to the cutting position.
In another preferred embodiment the blade segments are provided with transverse slots which when placed side-by-side define a channel for receiving an elongated force distribution means in the form of a spring steel member. The spring steel member is biased using coil springs such that it is urged in a direction tending to urge the blade segments into the resting position. The spring steel member distributes longitudinal pressure applied when the blade segments are displaced to the cutting position. The distributed forces cause a plurality of adjacent blade segments to make contact with the workpiece prior to cutting. This results in improved performance and reduced force requirements in some applications.
The trimming apparatus employs a roller disposed adjacent to the end of the blade segments opposite the cutting blade. Included is a means for moving the roller along the line of the contour, to cause the roller to sequentially contact the edges of the blade segments. A mechanical or fluid pressure means is provided for applying a force on the roller, to cause the roller to exert longitudinal pressure on the blade segments as the roller is moved along the line of the contour. This cause the roller to sequentially force the blade segments into cutting contact with the workpiece.
The method of cutting is capable of trimming through at least three folds of vinyl, plastic or cloth covering without scoring or damaging the substrate beneath. The blade pressure is preferably on the order of 60 pounds per 100/1,000th of linear width of the cutting blade. A urethane roller provides a resilient surface which takes up excess pressure. The invention can follow curved contours about flat workpieces and also about nonflat workpieces. The invention is thus well adapted for trimming vacuum formed vinyl vehicle interior parts.
For a more complete understanding of the invention, its objects and advantages, reference may be had to the following specification and to the accompanying drawings.